Sliding bearing is surface contact, so the contact surface to maintain a certain oil film, so the design should pay attention to the following issues:
1, so that the oil film can smoothly enter the friction surface.
2. The oil shall enter the bearing from the non-bearing area.
3. Do not open the whole annular oil tank in the middle of the bearing.
4, such as oil brick, seam opening oil groove.
5, make oil ring to oil is completely reliable.
6. Do not plug the oil hole.
7, do not form the oil flow area.
8. Avoid cutting off the sharp edges and edges of the oil film.
Sliding bearings can also be lubricated with grease. The following points should be considered when selecting grease:
(1) when the bearing load is low, a small amount of grease should be selected to permeate, and vice versa.High speed bearings are used for low tapping, high oil stability grease.It is important to note that the base oil of the grease has a low viscosity.
(2) the choice of the grease generally higher than the working temperature of 20-30 ℃, under the condition of continuous operation under high temperature, be careful not to exceed the permitted use of grease temperature range.
(3) when working in water or wet environment, sliding bearing should choose good water resistance, calcium, aluminum or lithium grease.
(4) use good adhesion of grease.
2. Choice of sliding bearing grease:
Load < 1 mpa, shaft neck circumference speed below 1 m/s, the highest working temperature is 75 ℃, choose a third type of grease on the calcium;
1-6.5 MPa, load speed shaft neck circumference of 0.5 5 m/s, the highest working temperature of 55 ℃, choose 2 calcium base grease;
Load > 6.5 MPa, under the shaft neck circumference speed 0.5 m/s, the highest working temperature 75 ℃, choose 3 calcium base grease;
Load < 6.5 MPa, shaft neck circumference of 0.5 5 m/s speed, the highest working temperature 120 ℃, choose two lithium grease;
Load > 6.5 MPa, under the outer circumferential speed 0.5 m/s, the highest working temperature 110 ℃, choose 2 calcium sodium calcium fat;
1-6.5 MPa, load under the shaft neck circumference speed 1 m/s, the highest working temperature of 50-100 ℃, choose 2 kinds of lithium grease;
Load > 5 mpa shaft neck circumference speed 0.5 m/s, the highest working temperature 60 ℃, choose 2 calendar grease;
In damp environment, 75-120 ℃ temperature conditions should be considered, the application of calcium - sodium fatty grease.In the humid environment, working temperature below 75 ℃, do not contain 3 calcium base grease, can also be used aluminum alloy grease.Working temperature at 110-110 ℃, using lithium grease or barium base grease.Concentrated lubrication, less consistency.
3. Grease lubrication cycle of sliding bearing:
Accidental work, important parts: shaft speed <200r/min, lubrication cycle once every 5 days;Axial speed > 200r/min, lubrication cycle once every 3 days.
Intermittent operation: shaft speed <200r/min, lubrication cycle 2 days;Shaft speed > 200r/min, lubrication once a day.
Continuous operation, working temperature is less than 40 ℃ : shaft speed < 200 r/min, the lubrication cycle once a day;Axial speed > 200r/min, lubrication cycle once.
Continuous running, working temperature of 40-100 ℃ : shaft speed < 200 r/min, the lubrication cycle time;Shaft speed > 200r/min, lubrication cycle twice.
It is necessary to make the journal and sliding bearing uniform, good contact, but also a certain clearance.
The Angle between the contact point and the center of the journal and the sliding bearing.The contact Angle should not be too large or too small.If the contact Angle is too small, the pressure of the sliding bearing will be increased, and if it is serious, the sliding bearing will produce greater deformation, accelerate the wear and shorten the service life.If the contact Angle is too large, it will affect the formation of oil film, and the liquid lubrication is not good.
Experimental research shows that the contact Angle of sliding bearing limit is 120 °.When the sliding bearing is worn to the contact Angle, the liquid lubrication is destroyed.Therefore, the sliding bearing is no longer affected under pressure, and the contact Angle is as small as possible.As can be seen from the theoretical analysis of friction, when the contact Angle is 60 °, minimum friction torque, so the speed of the sliding bearing is higher than 500 r/min, contact Angle 60 °, speed is less than 500 r/min, can contact Angle is 90 ° and 60 °.